Field of the Invention
The present invention relates to a contactless power transfer system and a power transmission device, and particularly to a technique for protecting, when an abnormality occurs, a contactless power transfer system that transfers electric power in a contactless manner between a power transmission device and a power reception device.
Description of the Background Art
Conventionally, contactless power transfer systems transmitting electric power from a power transmission device to a power reception device in a contactless manner are known (see Japanese Patent Laying-Open Nos. 2013-154815, 2013-146154, 2013-146148, 2013-110822, 2013-126327, and 2003-209903). The power transmission device includes a power transmission coil, and the power reception device includes a power reception coil.
For example, in a contactless power feeding system disclosed in Japanese Patent Laying-Open No. 2003-209903, a contactless power feeding device (power reception device) includes a resonant circuit unit, a power reception unit, and an output voltage restriction unit. The resonant circuit unit receives electric power in a contactless manner from an AC power supply. The power reception unit outputs electric power supplied from the resonant circuit unit to a motor. When an output voltage of the power reception unit becomes more than or equal to a reference voltage, the output voltage restriction unit causes electric power from the resonant circuit unit to be supplied to a shunt rather than a main path along which electric power is supplied from the resonant circuit unit to the power reception unit. Accordingly, electric power supply from the resonant circuit unit to the power reception unit is interrupted, and the output voltage of the power reception unit decreases. As a result, with this technique, an excess of the output voltage of the power reception unit can be avoided, and damage to devices can be prevented.